Acoustic liners are generally used to suppress sound propagation from a noisy source. In the aerospace industry, for example, acoustic liners are often used to reduce the noise emanating from an aircraft engine and fan assembly. Typically, the aircraft engine and fan are housed within a nacelle enclosure, and acoustic liners are generally integrated within the nacelle structure. While acoustic liners can be fabricated from metal or composite materials, composites offer a number of advantages, such as weight reduction and improved fatigue resistance in a high sonic environment, among others. Composite acoustic liners are typically fabricated in a sandwich-type configuration, with a solid backsheet, a honeycomb sound-absorbing core middle section, and a perforated facesheet.
Composite acoustic liners for this type of noise suppression application are generally inspected by an ultrasonic technique, such as a “through-transmission ultrasonic” (TTU) process. One type of TTU inspection procedure, known as an ultrasonic squirter system, utilizes water streams that are directed against the outside surfaces of the article being inspected, in order to carry the ultrasonic inspection signal from an ultrasonic transmitter through the test article to an ultrasonic receiver. In the case of a composite acoustic liner TTU inspection, the perforated facesheet on the acoustic liner is generally masked with some type of taping material to prevent water from entering the honeycomb structure through the facesheet perforations, since the presence of water in the honeycomb structure can cause problems in the subsequent finish and assembly operations. After completing a TTU inspection, the masking material is typically removed manually, and discarded. For applications involving relatively large test articles, such as aircraft nacelle acoustic liners, the manual taping and tape removal processes can be labor-intensive, and may also result in the deposit of masking material residue on the acoustic liner surface, leading to a possible degradation in performance of the acoustic liner.
Accordingly, it is desirable to provide a mask for TTU squirter system inspection of an acoustic liner that is relatively easy to apply and relatively easy to remove, and that does not deposit residue on the surface being masked. In addition, it is desirable to provide a mask that can be repositioned (i.e., reused) for subsequent ultrasonic testing. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.